1. Field of the Invention
The present invention relates to liquid drop jet heads and ink jet recording apparatuses.
2. Description of the Related Art
An ink jet recording apparatus is used as a picture recording apparatus or picture forming apparatus such as a printer, facsimile, copy machine, or plotter. An ink jet head is used for the ink jet recording apparatus as a liquid drop jet head. The ink jet head includes a nozzle, a liquid room, and a driving means (pressure generating means). An ink drop is jetted out by the nozzle. The nozzle is connected to the liquid room. The liquid room is called a pressurized liquid room, pressure room, jet room, or ink channel. The ink in the liquid room is pressurized by the driving means (pressure generating means). The ink drop is jetted out from the nozzle due to the pressure in the liquid room generated by the pressure generating means. Although there are several types of liquid drop jet heads such as a liquid drop jet head jetting a liquid resist as a liquid drop or a liquid drop jet head jetting a test material of DNA as a liquid drop, the ink jet head will be described.
A piezo type ink jet head is known as an ink jet head. An electromechanical transducer element such as a piezoelectric element as a driving means generating pressure by which the ink in the liquid room is pressurized is used in the piezo type ink jet head. A vibration board that is capable of elastically deforming and forms a wall surface of the liquid room is deformed by a deformation of the driving means, so that the volume is decreased/pressure is increased in the liquid room and the ink drop is jetted, in the piezo type ink jet head. See Japanese Laid-Open Patent Application, No. 2-51734.
In the above mentioned ink jet head, the piezoelectric element is deformed by charging or discharging so that the vibration board coming in contact with the piezoelectric element is deformed. The pressure inside of the pressurized liquid room increases due to the vibration board deforming so as to contract the volume of the pressurized liquid room so that the ink drop is jetted from the nozzle. After the ink drop is jetted, the piezoelectric element is deformed so as to deform the vibration board and expand the volume of the pressurized liquid room.
One example of the above mentioned ink jet head is shown in FIGS. 1 and 2. FIG. 1 is a cross sectional view along a long side direction of the liquid room of the ink jet head according to the conventional art. FIG. 2 is a cross sectional view along a short side direction of the liquid room of the ink jet head according to the conventional art.
In this ink jet head, a pressurized liquid room 114 connecting to a nozzle 113 jetting an ink drop 122 and a common liquid room 119 supplying the ink through a connecting part 120 to the pressurized room 114 are formed by connecting the liquid room substrate 111 and the nozzle board 118, and a piezoelectric element 117 provided on a base board 112 is connected to an outside surface of the vibration board 116 forming a part of a wall surface of the pressurized room 114.
The vibration board 116 is elastically deformed based on a deformation of the piezoelectric element 117. However, the vibration board 116 generally has a smaller rigidity (larger compliance) than other walls forming the pressurized room 114. Furthermore, the common liquid room 119 is connected to an ink tank not shown in FIGS. 1 and 2. A support member 121 is provided between the liquid room board 111 and a base board 112.
The piezoelectric element 117 is deformed by applying a voltage from a driving circuit not shown in FIGS. 1 and 2 to the piezoelectric element 117 so that the vibration board 116 is deformed so as to increase or decrease the volume of the pressurized liquid room 114. In a case where the volume of the pressurized room 114 is increased, the inside pressure of the pressurized liquid room 114 is reduced so that the ink is filled up through a connecting part 120 from the common liquid room 119 to the pressurized liquid room 114.
After that a driving force is implemented so as to increase the inside pressure of the pressurized liquid room 114. That is, in a case where the piezoelectric element 117 is driven so as to reduce the volume of the pressurized liquid room 114, the inside pressure of the pressurized liquid room 114 is increased. Because of this, ink is pushed out from the nozzle 113 and sprayed as the ink drop 122 to adhere to a recording medium such as paper so that recording can be implemented.
Thus, the ink drop in the ink jet head using the vibration board is formed based on a deformation of the vibration board. A connection part with the piezoelectric element as a driving resource is an important factor as a capability for the ink jet head.
Because of this, as disclosed in Japanese Patent No. 3147132 or Japanese Patent No. 3070625, there is a technology wherein a convex part having an island shape for connecting with the piezoelectric element is formed on the vibration board.
A structure of the above mentioned conventional ink jet head is described with reference to FIG. 3 through FIG. 6. FIG. 3 is a perspective view of the conventional ink jet head. FIG. 4 is a expanded view of a part shown in FIG. 3. FIG. 5 is a perspective view of the vibration board of another example of the conventional ink jet head. FIG. 6 is a rough perspective view of the conventional ink jet head. In FIG. 3 through FIG. 6, parts that are the same as the parts shown in FIG. 1 and FIG. 2 are given the same reference numerals, and explanation thereof will be simplified.
In this ink jet head, a concave part 123 is formed at the vibration board 116 forming one of the wall surfaces of the pressurized liquid room 114 so that a concave part 123 is formed. A convex part 124 having as island shape is formed as a thick part at a position where the piezoelectric element 117 comes in contact with the vibration board 116. That is, the thin part 126 surrounds all of the convex part 124 having the island shape as a thick part with a substantially constant thickness.
The piezoelectric element 117 corresponds to the pressurized liquid room 114. The concave part 123, which surrounds the convex part 124 having the island shape that comes in contact with the piezoelectric element 117, is divided by the thick part 125. The thin part 126 is formed by the vibration board 116 shown in FIG. 5. The convex part 124 having the island shape is formed on the thin part 126 as a thick part.
It is possible to reduce the amount of vibration of the piezoelectric element 117 that is transferred to other neighboring pressurized liquid rooms by making the piezoelectric element 117 come in contact with the convex part 124 having the island shape and driving the piezoelectric element. Furthermore, it is possible to convert the deformation of the piezoelectric element to the change of the volume of the pressurized liquid room efficiently, namely by a pressure change.
However, according to the above mentioned conventional ink jet head, it is necessary for the convex part 124 having the island shape formed on the vibration board 116 to be formed having a constant distance from the border of the division of the pressurized liquid rooms 114. Accordingly, it is necessary to form the thin part 126 having a constant width surrounding the convex part 124 having the island shape. Hence, it is required to have higher measuring precision or positioning precision.
Furthermore, the long side of the convex part 124 having the island shape is a longer than the long side of the head end part of the piezoelectric element 117 In addition, it is necessary to provide space for the thin part 126 so that it is difficult to make the whole of the ink jet head small. Hence, there is a problem to correspond to an arrangement of pressurized liquid rooms 114 with a high density. Furthermore, since a change of the volume inside of the pressurized liquid room 114 is decided based on the size of the convex part 124 and the amount of the deformation of the piezoelectric element 117, it is necessary to make the dimensions of the convex part 124 with high precision. However, it is difficult to make the dimensions of the convex part 124 with high precision, so the yield rate is reduced and manufacturing cost is increased.
Furthermore, the vibration board 116 having a large area of the thin part 126 is one element of the pressurized liquid room 114. The pressurized liquid room 114 has small rigidity (large compliance) so that an efficiency to increase the inside pressure of the pressurized liquid room 114 is worse so that the controllability of a meniscus at the time of ink drop jetting declines.
In addition, when the piezoelectric element 117 is driven, a strain based on an elastic deformation occurs at the thin part 126 surrounding the convex part 124 having the island shape. The vibration board 116 may be broken due to the concentration of the stress occurring in conjunction with an unexpected condition such as scatter at the time of forming the convex part 124 and the thin part 126. In order to form a large number of the pressurized liquid rooms 114 without scatter, the manufacturing process becomes complicated so that various apparatuses are required to be improved and an increase of the cost may occur.
Accordingly, it is a general object of the present invention to provide a novel and useful liquid drop jet head and ink jet recording apparatus in which one or more of the problems described above are eliminated.
Another and more specific object of the present invention is to provide a liquid drop jet head by which the inside pressure of the liquid room can be increased and decreased without reducing the efficiency of the driving means, controllability of the meniscus and a capability of the jetting the liquid drop can be improved, the size of the liquid drop jetting head is made small, and occurrence of scatter can be reduced. It is also an object to provide an ink jet head recording apparatus in which the liquid drop jet head is used so that picture quality is improved.
The above object is achieved by a liquid drop jet head, including a nozzle jetting a liquid drop, a liquid room connected to the nozzle, a vibration board forming a wall surface of at least a part of the liquid room, driving means generating a pressure pressuring a liquid provided in the liquid room by coming in contact with the vibration board, a support substrate to which an end part of the driving means is connected without connecting to the vibration board, and a gap between the support substrate and the vibration board at a position corresponding to a partition of the liquid room, wherein the vibration board comprises a thin part and a thick part and the area of the thin part is divided by the thick part with which the driving means comes in contact.
The above object is also achieved by a liquid drop jet head, including a nozzle jetting a liquid drop, a liquid room connected to the nozzle, a vibration board forming a wall surface of at least a part of the liquid room, driving means generating a pressure pressuring a liquid provided in the liquid room by coming in contact with the vibration board, a support substrate to which an end part of the driving means is connected without connecting to the vibration board, and a support member connecting the support substrate and the vibration board at a position corresponding to a partition of the liquid room, wherein the vibration board comprises a thin part and a thick part and the area of the thin part is divided by the thick part with which the driving means comes in contact.
According to the present invention, it is possible to improve the rigidity of the liquid room and the controllability of drop jetting so that scatter can be reduced and a stable drop jetting capability can be achieved.
The thick part may project to a side where the driving means facing the liquid room comes in contact.
According to the present invention, a liquid flow in a side of the liquid room is prevented from being blocked.
The thick part may be provided along a long side direction of the liquid room.
According to the present invention, it is possible to improve rigidity of the liquid room and to better control the displacement amount of the vibration board.
The thin part whose area may be divided by the thick part has a long and narrow configuration along the long side direction of the liquid room.
According to the present invention, it is possible to better control the displacement amount of the vibration board.
The length of the thin part in the long side direction of the liquid room may be longer than the length of the driving means that comes in contact with the thick part in the long side direction of the liquid room.
According to the present invention, it is possible to control a change of the capability due to a contact position gap of the thick part and the driving means so that it is possible to better control the a displacement amount of the vibration board.
The area of the thin part may be formed at a symmetrical position from the thick part.
According to the present invention, deviation of the change of pressure inside of the liquid room is prevented so that it is possible to prevent mutual interference.
The thick part of the vibration board, surrounded by the thin part, may have a substantially constant thickness.
According to the present invention, it is possible to reduce manufacturing cost and obtain high precision.
The driving means may comprise a piezoelectric element whose displacement in a normal direction of the vibration board is in a d33 direction.
According to the present invention, it is possible to drive the liquid drop jet head at a high speed.
The piezoelectric element may have a structure in which a plurality of layers of piezoelectric elements and electrode layers are stacked, and an end part in the long side direction of the liquid room may have an inactive area where an electric field is not generated and which faces and comes in contact with the partition of the liquid room.
According to the present invention, it is possible to control a change of a capability due to a contact position gap.
The inactive area of the piezoelectric element may face and come in contact with the partition of both ends in the long side direction of the liquid room.
According to the present invention, it is possible to improve rigidity of the whole liquid drop jet head by having an inactive area function as a support member for the vibration board and the base substrate.
An active area of the piezoelectric element may not exist in an area facing the partition of both ends in the long side direction of the liquid room.
According to the present invention, vibration is prevented from giving the partition unnecessary displacement so that a block against displacement efficiency of the piezoelectric element is avoided.
The inactive area of the piezoelectric element may exist in an area facing a driving area of the vibration board.
According to the present invention, it is possible to prevent scatter of a capability against the position gap at the precise time of contacting.
The piezoelectric element may have a structure in which the length in the long side direction of the liquid room at a position where an end part of the piezoelectric element comes in contact with the vibration board is shorter than the length in the long side direction of the liquid room.
According to the present invention, it is possible to further improve head rigidity by increasing thickness of the liquid room at a part corresponding to surrounding a position where an end part of the piezoelectric element comes in contact with the vibration board more than the thickness of the thick part.
The piezoelectric element may have a structure in which the length of the piezoelectric element in the long side direction of the liquid room at a position where the piezoelectric element comes in contact with the vibration board is shorter than the length of the thick part of the vibration board in the long side direction of the liquid room.
According to the present invention, it is possible to contact the piezoelectric element with the thick part precisely.
The piezoelectric element may have a structure in which the length of the piezoelectric element in a short side direction of the liquid room at a position where the piezoelectric element comes in contact with the vibration board is longer than the length of the thick part of the vibration board in the short side direction of the liquid room.
According to the present invention, it is possible to reduce scatter due to a positioning gap at the time of contacting.
The thick part of the vibration board may comprise a first thick part with which the driving means comes in contact and a second thick part having a different thickness from the thin part and connected to the first thick part and the partition of the liquid room.
According to the present invention, it is possible to reduce rigidity of a part where the piezoelectric element does not come in contact and improve rigidity of the whole liquid room.
The above mentioned object is also achieved by an ink jet recording apparatus, including an ink jet head jetting the ink drop, the ink jet head including a nozzle jetting the ink drop, a liquid room connected to the nozzle, a vibration board forming a wall surface of at least a part of the liquid room, driving means generating a pressure pressuring a liquid ink provided in the liquid room by coming in contact with the vibration board, a support substrate to which an end part of the driving means is connected without connecting to the vibration board, and a gap between the support substrate and the vibration board at a position corresponding to a partition of the liquid room, wherein the vibration board comprises a thin part and a thick part, and the area of the thin part is divided by the thick part with which the driving means comes in contact.
According to the present invention, it is possible to stably record a picture having high quality.
Other objects, features, and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.